they follow the post to get notification when someone answers eg. tells the name of the manga someone has been looking for
They mean they liked the topic it was asked and would also want to know the answer to it
If you reply to a comment you will get a notification when someone else replies. So, If someone wants to stay updated on a comment of their interest, they will write 'following'.
Ohhh I understand now :) thank you all!
Why do people keep saying “following” on posts? I don’t get it haha